Failed to detect Next.js version. Using OpenNext v${DEFAULT_

Error message

Failed to detect Next.js version. Using OpenNext v${DEFAULT_OPEN_NEXT_VERSION} as default.

What it means

The Nextjs component inspects package.json to decide whether to use OpenNext v2 (Next.js 14) or the default OpenNext version. When the package.json cannot be read or parsed (or `next` cannot be resolved from dependencies/devDependencies), detectDefaultOpenNextVersion logs this console.warn and falls back to the default OpenNext version rather than failing the deploy.

Source

Thrown at platform/src/components/aws/nextjs.ts:596

    super(__pulumiType, name, args, opts);
  }

  protected normalizeBuildCommand(args: NextjsArgs) {
    return all([args?.buildCommand, args?.openNextVersion, args?.path]).apply(
      ([buildCommand, openNextVersion, sitePath]) => {
        if (buildCommand) return buildCommand;

        function detectDefaultOpenNextVersion() {
          try {
            const pkgPath = path.join(sitePath ?? ".", "package.json");
            const pkg = JSON.parse(fs.readFileSync(pkgPath, "utf-8"));
            const nextVersion =
              pkg.dependencies?.next ?? pkg.devDependencies?.next;
            if (nextVersion && isALtB(nextVersion, "15.0.0")) {
              return DEFAULT_OPEN_NEXT_VERSION_NEXT14;
            }
          } catch {
            console.warn(`Failed to detect Next.js version. Using OpenNext v${DEFAULT_OPEN_NEXT_VERSION} as default.`);
          }
          return DEFAULT_OPEN_NEXT_VERSION;
        }

        const version = openNextVersion ?? detectDefaultOpenNextVersion();
        const packageName = isALteB(version, "3.1.3")
          ? "open-next"
          : "@opennextjs/aws";
        return `npx --yes ${packageName}@${version} build`;
      },
    );
  }

  protected buildPlan(
    outputPath: Output<string>,
    name: string,
    args: NextjsArgs,
    { bucket }: { bucket: Bucket },

View on GitHub (pinned to a0bd20f762)

Solutions

Verify the component's `path`/`root` points to the directory containing the Next.js app's package.json
Ensure the app has `next` listed in dependencies (or devDependencies) with a valid semver version (e.g. "15.1.0") — replace placeholders like `workspace:*` or `file:` specs
Fix any JSON syntax errors in package.json (`npx jsonlint package.json` or `cat package.json | node -e 'JSON.parse(require("fs").readFileSync(0))'`)
Pin the OpenNext version explicitly: `sst nextjs.Nextjs(..., { openNextVersion: "3.x.x" })` to skip auto-detection and silence the warning

Example fix

// before (sst.config.ts, path misconfigured)
new sst.aws.Nextjs("Web", { path: "packages/webapp" }) // no package.json there
// after
new sst.aws.Nextjs("Web", { path: "apps/web" }) // apps/web/package.json has "next": "15.1.0"

Defensive patterns

Strategy: validation

Validate before calling

const pkg = JSON.parse(fs.readFileSync(path.join(appPath, "package.json"), "utf8"));
const next = pkg.dependencies?.next ?? pkg.devDependencies?.next;
if (!next || !semver.valid(semver.coerce(next))) {
  throw new Error(`package.json at ${appPath} has no valid semver "next" dependency; got: ${next}`);
}

Type guard

function isValidNextVersion(v: unknown): v is string {
  return typeof v === "string" && /^(\^|~|>=?)?\d+\.\d+\.\d+/.test(v) && !v.startsWith("workspace:") && !v.startsWith("file:");
}

Try / catch

try {
  const pkg = JSON.parse(fs.readFileSync(pkgPath, "utf8"));
  // use pkg.dependencies?.next
} catch (err) {
  console.warn(`Failed to detect Next.js version (${err}); set openNextVersion explicitly in sst.config.ts`);
  return DEFAULT_OPEN_NEXT_VERSION;
}

Prevention

Pin `next` to an explicit semver version in package.json — avoid workspace:/file:/latest specs
Set `openNextVersion` explicitly on the Nextjs component to bypass auto-detection
Confirm the component's `path` points at the folder containing package.json
Keep package.json valid JSON and committed to the deploy context (not gitignored)

When it happens

Trigger: Calling sst nextjs component construction (openNextVersion not explicitly set) while the app's package.json is missing, unreadable, malformed JSON, lacks a `next` entry in dependencies/devDependencies, or uses a non-semver `next` version string that breaks isALtB comparison inside the try block.

Common situations: Deploying a Next.js app whose package.json was not included (wrong `root`/`path` config pointing at a directory without package.json); monorepo paths misconfigured; a `next` version like `workspace:*` or a file: URL that the semver comparator rejects; deploying a Next.js 15+ app (returns default path but the catch still fires on parse issues).

Related errors

AI-assisted analysis of anomalyco/sst@a0bd20f762 (2026-08-30). Data as JSON: /api/errors/ed87d0d58b18022b. Report an issue: GitHub.